main {
  box-sizing: border-box;
  width: 100%;
  padding: 10px 20px;
  display: flex;
  justify-content: space-around;
  flex-wrap: wrap;
  border: solid 1px #fff;

}

div {
  background-color: #f6e58d;
  width: 200px;
  height: 200px;
  margin-bottom: 10px;
  border: solid 1px #fff;
  border-radius: 8px;
}

/* 矩形 */
.rectangle {
  width: 200px;
  height: 200px;
}

/* 三角形 */

.triangle {
  background: transparent;
  position: relative;
}

.triangle::before {
  content: '';
  width: 0;
  height: 0;
  position: absolute;
  left: 0;
  bottom: 0;
  border-bottom: #f6e58d 200px solid;
  border-top: transparent 200px solid;
  border-left: transparent 100px solid;
  border-right: transparent 100px solid;
}

.cicle {
  border-radius: 50%;
}

/* 平行四边形 */
.parallelogram {
  background-color: transparent;
  box-sizing: border-box;
}
.parallelogram::before {
  z-index: -1;
  content: '';
  position: absolute;
  width: 200px;
  height: 200px;
  border-radius: 6px;
  background-color: #00735f;
  transform: skewX(-6deg) translateX(-10px);
}
